Gas consumption is way too HIGH, Mileage too low

[RichV]

new parts and a new weekend to work on the bike.

I purchased the following parts:
1. Four new plugs
2. New jets
3. New plug caps

I also previously swapped out the coils with no change in performance.

So the initial results are:
1. Engine starts and idles high right off the bat. Adjusted the idle down to 1K and the idle hold with not stalling.
2. The carbs synced without an issue. only need some tweaks. The vacuum was stronger than before on all intakes.
3. The advance works properly now and does not "stick" at 2K RPM. It advances on acceleration and returns to 1K idle after.

Two hour test ride (110 miles) started out okay. Initially, I was happy with the results and the bike performed well. There was still a hint of hesitation but not enough to worry about. Accelerated evenly and at all RPMs.

After about an hour, problems started to occur in the low end of the RPM when starting out. There was a vibration and sound indicating that it was not all there. It was starting to run rough. Once above 3000 RPM it would even out but acceleration was starting to lag and the power was dropping off in the low RPMs.

I rode 120 miles and stopped to get gas half way and near the end. My mileage improved from 10 MPG to 20-23 MPG, Sucks for a bike but better than before.

So I got back home and pulled the plugs (see below). Plugs #1 and #4 still look fine (just like before) and #3 looks a lot better but still has some black deposits (not much). Plug #2 looks all fowled up. It was also wet so I could have some oil mixed in or it's just gas wet. Hard to tell. The threads also look a little blue.

So any help for moving forward would be greatly appreciated. Everything else on the bike works fine except for the left crank seal which is covered in a different thread. Right now it runs rough at low RPM when accelerating. All other problems appear to be fixed.

[GLoweVA]

I have to ask the stupid question, have you verified that you're running the correct TCI?
81s run the 4RO TCI, if i remember correctly. It has the curve programmed in, the older ones require the mechanical advance. IF you had an older TCI and no mechanical advance, then that may give you some of these same symptoms.

I might have a spare advance assembly around here somewhere.

Edit, had a thought about #2 plug fouling, that's the same # that the advance plugs into. Maybe there's something going on there.

[DiverRay]

I hate to say it, but IF you have the brass floats, pull the carbs again! Pull the #2 float, and shake it near your ear. If hear ANYTHING, test the float. Put the float in a pan of almost boiling water and hold it under with tongs or something( do this when SWMBO is NOT at home! ). If you see ANY bubbles, you have a leak. I had one float that took me a day to find the leak.
This is my $0.02, and from this distance it's all I can do. Good luck!

[GLoweVA]

I hate to say it, but IF you have the brass floats, pull the carbs again! Pull the #2 float, and shake it near your ear. If hear ANYTHING, test the float. Put the float in a pan of almost boiling water and hold it under with tongs or something( do this when SWMBO is NOT at home! ). If you see ANY bubbles, you have a leak. I had one float that took me a day to find the leak.
This is my $0.02, and from this distance it's all I can do. Good luck!

He's got an 81, so i hope he's got the plastic floats.

Another question is do the pilots towers have the crossover passages and need the plugs or not.

[TopCatGr58]

81's do NOT have the sharing tunnel, and the pilot jet towers are NOT to be capped with the rubber caps.

Rich, do another comp test, wondering if the rings may be partially stuck?

Can't remember if you have INLINE fuel filters....if not and just relying on the intank filter towers...that can be a source of crud that can cause a float needle to get stuck open causing that cylinder to flood.

Also, the 81 has the Press in float needle seats with O-rings. Did you replace the O-rings during the clean up?? Did you replace the float needles...they should be Viton tipped type. Did you trim/shave the float bowl gasket to ensure that it isn't sticking out too far catching the float and hanging it up?? Also ensuring that the #2 carb float moves easily on it's mounting pin.

T.C.

[RichV]

I have to ask the stupid question, have you verified that you're running the correct TCI?

I think I have the correct unit. Remember, I had two bikes from the same year and they both had the same box, just different serial number: 005 and 007 (two apart). Here are the photos of the one installed and the extra.

[RichV]

I hate to say it, but IF you have the brass floats, pull the carbs again! Pull the #2 float, and shake it near your ear. If hear ANYTHING, test the float.

It's a plastic float on the 81. I tested them before but the #1 float kept jamming so I replaced it with a spare and now it works fine. It was causing a gas flood out the air box but that stopped when I changed the float.

[RichV]

Rich, do another comp test, wondering if the rings may be partially stuck?

Can't remember if you have INLINE fuel filters....if not and just relying on the intank filter towers...that can be a source of crud that can cause a float needle to get stuck open causing that cylinder to flood.

Also, the 81 has the Press in float needle seats with O-rings. Did you replace the O-rings during the clean up?? Did you replace the float needles...they should be Viton tipped type. Did you trim/shave the float bowl gasket to ensure that it isn't sticking out too far catching the float and hanging it up?? Also ensuring that the #2 carb float moves easily on it's mounting pin.

T.C.

So many questions...

I will run the test when I return mid week. How do rings get stuck? I installed new ones after I started to have problems.

I have inline filters. I also have a vacuum fuel cutoff which stops the flow if the engine quits (and if I forget the turn the fuel off).

I replaced the seats, o-ring and needles. I tested the fuel levels in the bowls on the bench and on the bike using a clear fuel line. I will test them again when I return. The needles are viton tipped.

I trimmed the gasket and made sure the floats were all the right height and all lined up upside down and right side up.

They freely move (as near as I know).

[TopCatGr58]

Hey Rich,

I thought you had rescued this bike/engine, but I didn't remember whether you had done a honing or replaced the piston rings?? IT is the piston rings that I was thinking about sticking...compression but also OIL rings. THey can just get stuck from years of storage/lack of use and old fuel/oil gumming them up in the bores. Just as Kurt with his new rebuild.....he did a treatment of MMO and has regained a ton of compression that he thought was bad due to worn cylinders and rings, but it was just that they were STUCK....and NOW loosened, are reseating and sealing much better!!!

Another thing is the float needles, were they from the KIT, or original Mikuni? We have seen and learned from a recent thread about Jeff's carbs getting hands on help for them FLOODING, and found out that the K&L float needles and bodies are different, and can prevent the floats from reaching the sealing position causing flooding!? JAT!

T.C.

Here's that thread link set to the page where Schming found the float needle difference!!!

http://www.xs11.com/forum/showthread.php?t=43908&page=7

[RichV]

I did replace the rings and honed the cylinders.

I guess I can take the carbs out again and look at the float and needle. The were holding the fuel last time I checked.

[TopCatGr58]

After about an hour, problems started to occur in the low end of the RPM when starting out. There was a vibration and sound indicating that it was not all there. It was starting to run rough. Once above 3000 RPM it would even out but acceleration was starting to lag and the power was dropping off in the low RPMs.

I rode 120 miles and stopped to get gas half way and near the end. My mileage improved from 10 MPG to 20-23 MPG, Sucks for a bike but better than before.

So I got back home and pulled the plugs (see below). Plugs #1 and #4 still look fine (just like before) and #3 looks a lot better but still has some black deposits (not much). Plug #2 looks all fowled up. It was also wet so I could have some oil mixed in or it's just gas wet. Hard to tell. The threads also look a little blue.

Hey again,

Yeah, the threads of the plug do look a bit blue, and that could indicate excessive amount of heat.... however if that cylinder were running too rich, it could run a little cooler....or it could heat up more as the unburnt fuel is then continuing to burn as it leaves the exhaust??

Poor low rpm response does indicate a pilot circuit problem vs. better response at higher rpms. Taking the carbs off and recheck the pilot jet circuit for open/free flowing....but again it's got at least carbon fouling of the plug from ?too much fuel? Check to make sure the PILOT JET is snug... I had helped MadMax one time, and surprisingly his pilot jet worked loose and fell out, and caused similar symptoms....because it was sucking unmetered fuel thru the Pilot jet tower's access to the fuel bowl!

IF that carb isn't flooding, then it falls back to lack of spark on that cylinder...a bit more rare than on the pair for that coil, but still happens. I know fresh plug caps/plugs....and you had tried the other coils without any change...but IF the coil is weak...either lack of full voltage TO it, or damage internally that might not show up until after it heats up....then it may not be putting out enough juice to fire both plugs....gets the first one, but not enough ooomph to get thru the engine and then back up the other plug.

After rechecking what we've discussed....I would swap the plug wires with #2 and #3, NEW plug or known good burning used plug, and retest ride. IF the problem then develops in the #3 cylinder and #2 burns good and clean, then it's NOT the carbs but the COIL itself probably internally damaged or the wire to that cap is damaged. Then just replace the coil!

T.C.

[RichV]

T.C. I have two sets of coils. Can I use the 1-4 coil that I know works in the 2-3 position (connected to the 2-3 plug)?

So my check list is:
1. Check compression.
2. Check #2 float, needle, pilot jet, etc.
3. Swap 2-3 (or coil)

[DiverRay]

Yes, you CAN switch the coils to test them. If the plug wires are long enough, switch them and switch the Orange and Grey wires at the coils. You will now be running the 1&4 coil to fire the 2&3 plug.

[RichV]

Okay, here is what I've done/seen so far.

1. Engine compression on #1, #3 and #4 are at 120-125. The compression on #2 is at 115. These are low numbers but considering I just changed the rings they could rise once they get set. They are lower numbers than before I changed them (and my problems still existed).

2. I swapped out the coil for #2-#3. Runs fine at idle like it did before so I won't know if this had an affect until a test ride.

3. I checked the floats by leveling the bike, connecting the clear tube to the bottom and running the engine. In all cases, the level stayed at the bottom end of the height of the screw head on the bowl. I even shook the bike and it stayed at that height for all 4 carbs.

4. My left seal started to leak a couple of weeks ago and I ordered a replacement. I installed it earlier in the week and the oil held statically. On the test ride, it leaked again.

5. I removed the plug below the timing cover to make sure the o-ring was intact. The drained oil had a funny look to it. Darker than new, which I expected and lower in viscosity which I didn't. A smell test resulted in a hint of gas but I have been messing with carbs so I may not be smelling it correctly. I currently have 200 miles on the current oil change and the new rings and 100 miles on the jet change and float fix.

6. The oil leak out of the exhaust returned. Not alot but enough to produce some smoke when the engine warms up. goes away after a few minutes.

So my thought is that gas got into the oil during the period I was dealing with the bad jets and floats resulting in a lower viscosity oil. This, in turn, causes the oil to get past the rings and fowls the plugs, mostly #2. If I change the oil, maybe I'll see an increase in performance/compression and the oil leaks go away.

Does this sound reasonable? Should I use a different grade of oil? I'm using 30W-50 regular oil. I'm not an expert but I would expect the gas in the oil would cause the oil to pass through all kind of seals and rings.

[RichV]

Sorry but I meant 20W-50 motor oil.